Warm-up Period

[YarisHybrid2016]

In one of the threads recently was some discussion of the warm-up period, and whether it is better to let the car warm up prior to driving, or just get in and drive.

I did some experiments today (I was doing some good runs of about 30 miles each) so I allowed the car to warm up on the driveway before setting off (OAT 12 C). By a reference point 5 miles down the road I was already seeing a significant improvement (45 MPG vs. 39-41 MPG).

By the time I finished a journey I do quite often, the computer was reporting 59 MPG (previously I struggled to get 52). This run was the most representative as I was doing 60-70 MPH most of the way as usual.

Next journey, the car was pretty warm (it had been sat for an hour, OAT now 18 C). By the time I finished, the computer reported 71 MPG. A full 10 MPG better than before. Again, I let it idle before driving.

Third journey, it reported 68 MPG (previously about 58 MPG) though on this journey, traffic meant speeds around 50 MPH, instead of 60 MPH.

When I got home, it was reporting 55 MPG (previously around 50-52) but this was a bit of a bad test as I had floored it out of a road junction and was generally not trying for economy.

That said, I have never seen such high consecutive MPG figures as this. I doubt this was a total fluke. More journeys are definitely required to test the theory.

[offashead]

Very interesting. The problem with all this is. Unlike most vehicles? the hybrids don't have any way of telling me/us when the engine is warm or not, there is no dial to tell me. Some people I know tell me new cars have this info dial missing. To me, the info on engine temp has always been important. So why is it missing?

[YarisHybrid2016]

I think because ECUs are such that they are increasingly trusted to monitor the engine, and only alert the driver to when there is a problem (e.g. overheat). Knowing the coolant temperature is now considered obsolete, along with things that used to be on much older cars, like oil pressure (there is only a light for this).

As the driver you will also know if you last drove the car yesterday, or 5 minutes ago, and whether the engine ran in that period.

[offashead]

I think because ECUs are such that they are increasingly trusted to monitor the engine, and only alert the driver to when there is a problem (e.g. overheat). Knowing the coolant temperature is now considered obsolete, along with things that used to be on much older cars, like oil pressure (there is only a light for this).

As the driver you will also know if you last drove the car yesterday, or 5 minutes ago, and whether the engine ran in that period.

I still think that the gauge should exist. I don't trust the ECU as much as a gauge. I like old school stuff.

[timberwolf]

I think a temperature gauge would be a source of worry because a hybrid can run with a pretty cold engine. I've got a Scangauge 2, and I've seen engine coolant temperatures in the low 40's C when I was stuck in stationary traffic in winter with the engine just periodically cycling on and off.

[MEP's Yaris GS]

Very interesting. The problem with all this is. Unlike most vehicles? the hybrids don't have any way of telling me/us when the engine is warm or not

They do in as far as the ICE won't shut down if its not 'warmed up' :)

[offashead]

Due to a miserable virus I haven't been at work for a week or so. I have used the car during this period for short journeys and have noted a drop in mpg. Down from 64 to 46 mpg. The engine has been running quite a lot more during this period, rarely do I get into ev mode. During this time I have been leaving the car to do a warm up period.

Example. Power on, ready mode, engine engages, disengages after a minute or so, reverse off drive, drive to the bottom of road ( EV on), enter main rd, engine engages and pretty much stays on till I get to my destination, 1 or 2 miles away. Of course the temperature has dropped quite considerably since a couple of weeks ago and I would expect any car to drop mpg when doing short runs.

When I do get back to work things should improve, I will keep trying the warm up cycle as above.

[Wayne2015]

In one of the threads recently was some discussion of the warm-up period, and whether it is better to let the car warm up prior to driving, or just get in and drive.

I did some experiments today (I was doing some good runs of about 30 miles each) so I allowed the car to warm up on the driveway before setting off (OAT 12 C). By a reference point 5 miles down the road I was already seeing a significant improvement (45 MPG vs. 39-41 MPG).

By the time I finished a journey I do quite often, the computer was reporting 59 MPG (previously I struggled to get 52). This run was the most representative as I was doing 60-70 MPH most of the way as usual.

Next journey, the car was pretty warm (it had been sat for an hour, OAT now 18 C). By the time I finished, the computer reported 71 MPG. A full 10 MPG better than before. Again, I let it idle before driving.

Third journey, it reported 68 MPG (previously about 58 MPG) though on this journey, traffic meant speeds around 50 MPH, instead of 60 MPH.

When I got home, it was reporting 55 MPG (previously around 50-52) but this was a bit of a bad test as I had floored it out of a road junction and was generally not trying for economy.

That said, I have never seen such high consecutive MPG figures as this. I doubt this was a total fluke. More journeys are definitely required to test the theory.

Wow !

If this is true - does the user manual say the same thing ???

If not then why not ???

[YarisHybrid2016]

Wow...

Went out again today (12 miles each way). Let the car warm up first... 65 MPG (previously about 55-58 MPG) on the way out, 58 MPG on the way in (previously about 52 MPG).

The ultimate test of all this is going to be the tank average as always, but this is too co-incidental.

Ignoring the actual MPG figures, it seems this is resulting in about a 10% increase in efficiency on "local journeys".

Something I noticed is this is allowing EV mode to be available MUCH earlier in the journey. Where I'm slowing for corners, previously the engine would keep running, but now it engages EV mode during deceleration. It is also allowing me to drive in EV mode (not the EV MODE) almost from the start of the journey, whereas before it wouldn't let me as it was in the warm-up.

Thinking about the timings involved, I'm wondering if the engine is running for less time/warming up more effectively by the car being stationary, vs. when driving, it is a cold engine, with cold air moving around it, meaning it is taking longer, and the car generally is running less efficiently (unable to use EV mode in addition to the extended warm-up time).

So others can try the same methodology:

When starting from cold, get in, start the car as normal, but whilst in Park, before moving, just press the accelerator so the engine starts. Wait for the engine to stop, then drive.

[Wayne2015]

Just to get this right:

1. Are u driving in EV, ECO or NORMAL mode?

- I mean are either the ECO or EV buttons pressed?

2. So u start car and tough gas pedal just to start the engine up?

- then drive off immediately?

3. Are u ever in the PWR bands during these few test drives?

4. So u don't sit in the car and WAIT for the engine to start (but force it to start with touch of gas pedal)?

I think what u discovered is fantastic!

U need to BLOG it on Toyota website!

Tell Toyota UK!

Just surprised there is no such mentioned in the user manual :(

I did check last night ...

[monya]

Seems logical that a warm engine will achieve better mpg than a cold one including hybrids, so sitting in the car with the engine running for a few mins. before moving should improve mpg over short distances. Just as well these are petrol engines as I can't stand those with diesels sitting around stationary polluting the air.

BTW the new Auris seems to warm up faster than the Mk.1 which is good news for short journey folk.

[Hybrid-Harry]

I was a vehicle tech for over 45 years until I retired, and in the early years it was instilled in me that I should never warm up an engine before driving away. The reason for this was to keep totally cold oil from clogging up around the piston rings and the excess fuel used on keeping a cold engine from stalling, would wash away that oil into the crank case diluting the rest and carrying the carbon with it to blacken the colour faster.

However in my opinion modern vehicles have far tighter tolerances on moving parts, oil has a far better properties and fuel injection is far more efficient than a carburettor. So, with these in mind I can see no harm being done to the engine by warming it up first providing you drive away after.

Where you will do you fuel economy no good is warming up an engine a little bit and then switching it off without driving it away because if it's allowed to cool down the excess fuel device will trip in again and inject a higher rate of fuel until it warmed up again.

Just remember, low-temperature running is rich running whether it be warming up statically or on the move.

[offashead]

Wow...

Went out again today (12 miles each way). Let the car warm up first... 65 MPG (previously about 55-58 MPG) on the way out, 58 MPG on the way in (previously about 52 MPG).

The ultimate test of all this is going to be the tank average as always, but this is too co-incidental.

Ignoring the actual MPG figures, it seems this is resulting in about a 10% increase in efficiency on "local journeys".

Something I noticed is this is allowing EV mode to be available MUCH earlier in the journey. Where I'm slowing for corners, previously the engine would keep running, but now it engages EV mode during deceleration. It is also allowing me to drive in EV mode (not the EV MODE) almost from the start of the journey, whereas before it wouldn't let me as it was in the warm-up.

Thinking about the timings involved, I'm wondering if the engine is running for less time/warming up more effectively by the car being stationary, vs. when driving, it is a cold engine, with cold air moving around it, meaning it is taking longer, and the car generally is running less efficiently (unable to use EV mode in addition to the extended warm-up time).

So others can try the same methodology:

When starting from cold, get in, start the car as normal, but whilst in Park, before moving, just press the accelerator so the engine starts. Wait for the engine to stop, then drive.

May I ask. Has the heating been on in the car when doing the warm up cycle? Being the weather will eventually start getting colder I would imagine putting the heating on during the cycle is something one would do. Just wondering if this would make a difference to the time of the cycle period.

I did try the warm up today ( without heating) Only went a few miles though so no data to report.

[Wayne2015]

Anymore updates, Buddy???

As the winter temp settles in - be real money-saving scheme if your method does add on an whopping EXTRA 10mpg to the economy :)

[YarisHybrid2016]

Regarding the heating: being climate control it does its own thing, though now it is a bit cooler I find I run with it set at 16 C.

I run single-zone, AC on, auto mode, with the car in Eco Mode. If I need to get warm, I found switching the system OFF in the day is a good way to do that. If I'm in slow traffic and feel comfortable I will also switch it off to help extend the time running in EV mode.

I found that almost independent of HV Battery charge state, if the AC/heater demands power, the engine will start to service demand.

@Wayne2015: I'm going out today so will test further! It will have about 4 hours cooldown in between.

[Whitewagon]

The question is does the computer only work out the mpg when the car is moving? If so the fuel used during stationary warm up won't be included in the calculation so a tank to tank calculation is needed to prove this.

[MEP's Yaris GS]

The question is does the computer only work out the mpg when the car is moving? If so the fuel used during stationary warm up won't be included in the calculation so a tank to tank calculation is needed to prove this.

No it's any fuel used, stationary or moving.

[YarisHybrid2016]

Well something is definitely improving... I have just over half tank indicating on the fuel quantity indicator, and driven 211 miles so far.

Allowing for the bottom of the fuel guage meaning still 5 L in the tank (an experience I don't wish to repeat), so far this tank appears to be averaging over 60 MPG, and not allowing for the guage indicating over half.

[Wayne2015]

Well something is definitely improving... I have just over half tank indicating on the fuel quantity indicator, and driven 211 miles so far.

Allowing for the bottom of the fuel guage meaning still 5 L in the tank (an experience I don't wish to repeat), so far this tank appears to be averaging over 60 MPG, and not allowing for the guage indicating over half.

Awesome!

I tried a few times, to start up, dabble the gas pedal (engine came on) and then waited....

But how long do u wait before engine cuts out and then u drive off?

Coz I waited about a minute and the engine was still on, so I just drove off....

[YarisHybrid2016]

Hi,

Given that it is getting colder now (yesterday when I started it was 8 C), it depends a bit if the AC/heater is on. What I tend to do is switch the climate control OFF whilst waiting for the engine warm-up cycle, so the engine isn't running simply due to power requirements (though of course if the heater/demist is really needed, then use them as normal).

I think it takes a bit longer than a minute. Perhaps in summer this might be true, but as it gets colder, it will obviously take longer.

I noticed something interesting yesterday whilst sat in traffic. HV Battery was getting low due to running in EV mode for a while. Whilst the vehicle was stopped, the engine started up. With the vehicle stationary, the engine reached what sounded like idle, then increased in RPM, I presume to generate power to recharge the HV Battery. I then gently released the footbrake to creep forwards, and noticed instantly that the engine RPM dropped to what sounded like idle. The engine was clearly pulling the car (I noticed it pulls very slightly better whilst the engine is running). As soon as the vehicle stopped, the engine changed RPM back to the higher running RPM. After what seemed like a couple of minutes, the engine shutdown again.

I also have a theory about why sitting during the initial warm-up appears to use significantly less fuel: if the engine is over-fuelling because it is cold, then by driving in this state, requires even MORE fuel, and I think also the timings are altered as well, so the engine is not running as efficiently as it could (the purpose being to get everything warmed up as quickly as possible - IIRC one of the goals of this initial warm-up is high EGT to get the catalyzer up to temperature for emissions).

I'm thinking that if trying to drive in this period on top of the warm-up, it is the equivalent of harder acceleration, but due to modified timings, the efficiency is reduced, and so the engine doesn't appear to have any more performance despite the higher fuel burn.

The inefficiency/higher fuel burn over the first couple of minutes of driving during the warm-up is perhaps using fuel equivalent to hard acceleration at any other time.

Another side-effect is that once this initial warm-up period is completed, the car is much more willing to enter EV mode during deceleration, whereas when driving from cold, it won't do this. For me, within 2 miles, I have 4 places the car is slow enough to run in EV mode whilst I navigate some corners, and about 100 yards between two corners where I can run entirely in EV mode. When driving during the warm-up period, the engine doesn't stop during this period, whereas if I wait, it will.

I think all of these effects combined are what is making the significant difference (when you also consider that this covers nearly 2 miles of a 12 mile journey, or 18% of the distance!).

If you're setting off on a 100 mile journey, then the warm-up period probably represents such a small percentage of the journey time that you wouldn't notice, but on these shorter runs, it makes a big difference.

Does anyone have a way of seeing the actual fuel flow (e.g. L/min) whilst the vehicle is stationary?

[YarisHybrid2016]

I just checked the owners manual, and it just states that engine warm-up isn't necessary as it does this on its own. It also says lots of short journeys will hurt fuel economy as the engine warms up, but then cools again, necessitating warm-up again.

[Wayne2015]

Hi,

Given that it is getting colder now (yesterday when I started it was 8 C), it depends a bit if the AC/heater is on. What I tend to do is switch the climate control OFF whilst waiting for the engine warm-up cycle, so the engine isn't running simply due to power requirements (though of course if the heater/demist is really needed, then use them as normal).

I think it takes a bit longer than a minute. Perhaps in summer this might be true, but as it gets colder, it will obviously take longer.

I noticed something interesting yesterday whilst sat in traffic. HV battery was getting low due to running in EV mode for a while. Whilst the vehicle was stopped, the engine started up. With the vehicle stationary, the engine reached what sounded like idle, then increased in RPM, I presume to generate power to recharge the HV battery. I then gently released the footbrake to creep forwards, and noticed instantly that the engine RPM dropped to what sounded like idle. The engine was clearly pulling the car (I noticed it pulls very slightly better whilst the engine is running). As soon as the vehicle stopped, the engine changed RPM back to the higher running RPM. After what seemed like a couple of minutes, the engine shutdown again.

I also have a theory about why sitting during the initial warm-up appears to use significantly less fuel: if the engine is over-fuelling because it is cold, then by driving in this state, requires even MORE fuel, and I think also the timings are altered as well, so the engine is not running as efficiently as it could (the purpose being to get everything warmed up as quickly as possible - IIRC one of the goals of this initial warm-up is high EGT to get the catalyzer up to temperature for emissions).

I'm thinking that if trying to drive in this period on top of the warm-up, it is the equivalent of harder acceleration, but due to modified timings, the efficiency is reduced, and so the engine doesn't appear to have any more performance despite the higher fuel burn.

The inefficiency/higher fuel burn over the first couple of minutes of driving during the warm-up is perhaps using fuel equivalent to hard acceleration at any other time.

Another side-effect is that once this initial warm-up period is completed, the car is much more willing to enter EV mode during deceleration, whereas when driving from cold, it won't do this. For me, within 2 miles, I have 4 places the car is slow enough to run in EV mode whilst I navigate some corners, and about 100 yards between two corners where I can run entirely in EV mode. When driving during the warm-up period, the engine doesn't stop during this period, whereas if I wait, it will.

I think all of these effects combined are what is making the significant difference (when you also consider that this covers nearly 2 miles of a 12 mile journey, or 18% of the distance!).

If you're setting off on a 100 mile journey, then the warm-up period probably represents such a small percentage of the journey time that you wouldn't notice, but on these shorter runs, it makes a big difference.

Does anyone have a way of seeing the actual fuel flow (e.g. L/min) whilst the vehicle is stationary?

Ref in EV mode and stationary....my did the same, but, it pop-up a message "EV disabled..."

[Wayne2015]

Gave my car a go following this thread:

1. Power on (47.1 mpg shown)

2. Switch all electrics off (air con, stereo etc)

3. Dab at gas peddle (engine started)

4. Waited what seems forever, engine stopped

5. Drove off and display showed 46.8mpg - eeek!

Continued to drive as I used to...back to 46.9 mpg - no change for me :(

Will do more tests on a full tank sometime...

[offashead]

Ok folks an update. Went back to work today, got in the hybrid started up, fuel gauge read 49mpg. I drove off after a minute ICE still engaged, drove around , did a few jobs, perhaps 5 miles, fuel consumption 52 mpg. I stopped and did an update ( cleared last and trip) and started again. 100 miles later including a 20 mile M way trip I ended up with 75.9 mpg for the 100 miles.( eco mode- car in ready mode most of the day apart from a quick walk round town)

The question is. If I hadn't done the reset I don't think the fuel figure above would have been reached?

So it may be worth doing an experiment. Drive off as normal, hardly any warm up, stop after a couple of miles, reset and see what happens.

[PeteB]

...The question is. If I hadn't done the reset I don't think the fuel figure above would have been reached?

So it may be worth doing an experiment. Drive off as normal, hardly any warm up, stop after a couple of miles, reset and see what happens.

I tend to reset the B Trip meter every time I fill up (and log it in my database) so that I've got an overall mpg per tankful. I use the A trip for daily or individual journey mpg. Often if I fill on the way home, and the engine is already fully warmed, when I arrive home I might even see mpg in the 90s.

On a 120-150 mile run, where the warmup period is a much less significant part of the journey mpg, I've regularly seen upper 70s and occasionally low 80s (bear in mind the computer display is usually around 4 mpg optimistic based on tank to tank calculations).

[on the Gen 1 Prius there was a separate trip log on the MFD graph display which automatically reset when al least 2 gallons were pumped into the tank, in addition to the A & B Trip meters].